This Phase 3 trial is a randomized, double-blind, placebo-controlled trial of gemcitabine in combination with TH-302 compared to gemcitabine in combination with placebo in subjects with locally advanced unresectable or metastatic pancreatic adenocarcinoma. Randomized subjects will receive TH-302 plus gemcitabine or gemcitabine plus placebo in 4-week cycles until there is evidence of progressive disease, intolerable toxicity, or the subject discontinues from the trial for other reasons (for example, withdrawal of consent). The primary efficacy endpoint is overall survival (OS) time. The data cut-off for statistical analyses of the primary and secondary endpoints will be reached when 508 events (deaths) will be reported. No planned interim analyses will be conducted. An Independent Safety Monitoring Board (ISMB) will provide periodic evaluations of the unblinded safety data to ensure subject safety and the validity and scientific merit of the study. A total of 660 subjects will be enrolled.